The purpose of this research proposal is to test a model of collective decision-making in a situation called the N-person Prisoner's Dilemma Game (the NPD). In this situation, each person in the group is faced with a conflict between maximizing personal gain (individual interests) and maximizing mutual gain (social welfare). Yet, if everyone attempted to maximize their selfish interests, everyone would be worse off than if everyone cooperated and attempted to maximize the social welfare. The NPD is a prototype of many critical problems facing society and from a long-range perspective, empirical studies of the NPD may provide valuable insights into the nature of cooperative behavior in such real-life situations. The second purpose of the reseach is to determine the effects of several variables hypothesized to facilitate or inhibit cooperation in dilemma-type situations. The effects of two types of variables will be manipulated: (a) partitioning a large group of individuals into a small number of subsets (coalitions), such that each subset must reach a group decision to cooperate or to compete; and (b) the nature of prior experience in the situation.